This project will attempt to meet the following goals during the 1980-1981 tenure: 1. Determine the in vitro efficiency of ATP utilization by the nitrogen-fixing system of Clostridium pasteurianum, Klebsiella pneumoniae and Azotobacter vinelandii. 2. Examine in detail the effect of adenylates (ATP, ADP and AMP) on the efficiency of the utilization of ATP by the N2-fixing system. 3. Determine if during the utilization of ATP by nitrogenase a phosphorylation has occurred, i.e., what mechanism accounts for the ATP hydrolysis. What is the function of ATP? 4. Identify and characterize the Mo-containing species involved in the synthesis of the MoFe protein of nitrogenase. Establish the sequence of this synthesis. 5. Continue the X-ray analysis of crystals of the MoFe protein of Clostridium pasteurianum and Azotobacter vinelandii. Collect "native" data on crystals and initiate preparation of heavy metal derivatives.